pinctrl: uniphier: fix members of rmii group for Pro4

The ether_rmii_groups should have "ether_rmii" and "ether_rmiib" as
members. This patch replaces to them.

Fixes: 1e359ab1 ("pinctrl: uniphier: add Ethernet pin-mux settings")
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>